1. Field of the Invention
The present invention generally relates to a turbine for transferring energy from a fluid current. More particularly, the present invention relates to a turbine assembly having uniquely configured inverted tear drop shaped vanes or blades for reacting to a fluid current driven thereagainst and transferring said reaction to a centralized rotatable shaft.
2. Description of Prior Art
U.S. Pat. No. 4,293,274 ('274 Patent), which issued to Gilman, discloses a Vertical Axis Wind Turbine for Generating Usable Energy. The '274 Patent describes a wind turbine for converting wind forces into usable energy having a main shaft rotatably mounted in the axis of rotation for the wind turbine, and a pair of coacting complementary longitudinally extending vane members are connected to each other by a plurality of support and transmission assemblies in the form of articulated members and to the main or driven shaft for driving engagement thereof.
The coacting vane members of the device shown in the '274 Patent may either have straight side edges or preferably have spiralled or helically shaped side edges which in the closed position are aligned and in abutment with each other to define and form a right circular cylinder in side elevation. The vanes are movable between a normally open starting position and a closed position to vary the total vane surface available for contact by the wind forces acting at any given time when the wind turbine is in operation.
Articulated members of the support and transmission assemblies are pivoted to permit translational or side wise movement to and fro of the complementary vanes transverse relative to each other and the vertical axis through the main shaft, and pivotal cross members on each of the articulated support and transmission assemblies are vertically linked together to simultaneously alter the articulated members during such movement.
The respective complementary and cooperating vanes have their weight so distributed that centrifugal forces will act to move the complementary vanes towards the closed or right circular cylindrical form automatically as high rotational speeds result from excessive wind. Additionally the wind turbine as above described with resilient means to move the coacting cooperating vanes to the normally open starting position.
U.S. Pat. No. 5,405,246 ('246 Patent), which issued to Goldberg, discloses a Vertical Axis Wind Turbine with a Twisted Blade Configuration. The '246 Patent describes a vertical-axis wind turbine having two or more elongated blades connected to a rotor tower. The tower defines an axis of rotation and is linked, preferably via a gearbox or other torque-converting arrangement, to the shaft of a generator.
Each blade is “twisted” so that its lower attachment point is displaced angularly relative to its upper attachment point. In a preferred embodiment, the radial distance of each blade from the axis of rotation varies between upper and lower attachment points such that the blade lies approximately along a “troposkein”, which is the shape assumed by a string clamped at each end and spun about an axis passing through the ends of the string.
The ratio between blade chord length and blade thickness is preferably constant over the length of each blade, with the middle of each blade approximately 80% as thick as its ends. The cross-section of the blades may be teardrop-shaped, shaped as an airfoil, rectangular, or curved in some other way.
U.S. Pat. No. 6,465,899 ('899 Patent), which issued to Roberts, discloses an Omni-Directional Vertical-Axis Wind Turbine. The '899 Patent describes an omni-directional, vertical-axis wind turbine comprising a rotor/stator combination which maximizes energy production by increasing wind velocity and pressure plus eliminating back pressure. The stator section includes a plurality of vertical blades secured between upper and lower conical sails.
The blades have a radius fundamentally equal to that of the rotor and a chord length approximately 1.25 times its radius. The rotor has a diameter approximately equal to one-half that of the stator and has a plurality of concave blades secured to and spaced from a vertical spindle, said blades being arranged in stages within the vertical rise of the rotor. Each rotor blade has a chord line equal to twice its radii and a chord length approximating one-third the diameter of the stator.
U.S. Pat. No. 7,314,346 ('346 Patent), which issued to Vanderhye et al, discloses a Three-Bladed Savonius Rotor. The '346 Patent describes a Savonius style three bladed vertical axis wind turbine rotor has operational characteristics superior to those of conventional three bladed rotors. The blades have high curvature and a high skew factor, for example a curvature of greater than 7:1 (e.g. 2:1-5:1), and a skew factor of greater than 0.6 (e.g. 0.78-0.9).
The rotor also includes at least one vertical shaft, the blades operatively connected to the shaft. The rotor typically has an aspect ratio of at least 2:1. The rotor typically has a maximum power coefficient (Cp) of at least twice that of an otherwise identical rotor with a skew factor of 0.5 or less. The rotor can drive a generator with a drive which automatically increases the effective gear ratio as the rotational speed of the rotor increases; or the rotor can be connected to a propeller of a multihull wind powered boat.
U.S. Pat. No. 7,362,004 ('004 Patent), which issued to Becker, discloses a Wind Turbine Device. The '004 Patent describes a hybrid blade wind turbine device formed of at least a pair of straight outer airfoil blades, and a pair of inner helical wing blades, as supported for rotation within a safety protective cage structure, which wind turbine can be mounted in the vertical, horizontal, or other aligned operational positions.
The inner helical half wing blades, being preferably somewhat shorter than the length of the outer airfoil blades, act to “regularize” the swirling wind regime flowing through the hybrid wind turbine, so as to maximize the efficiency of the outer airfoil blades. The helical half wing blades can be formed of individual segmented vane segments to provide improved operational capabilities for the overall hybrid wind turbine. To best harness annualized available wind conditions, the hybrid wind turbine can be customized, through modification of the number of vane segments, the selection of the specific shape of the outer airfoil blades, and the specific operational positioning of the outer airfoil blades. Alternatively, the helical half wing blades can be formed as generally smooth-walled blades.
United States Patent Application Publication Number US 2007/0104582, which was authored by Rahai et al., describes a high efficiency vertical axis wind turbine having an optimized blade shape for increased torque output. The shape of the optimized profile includes a camber portion at a leading edge region of the blade with a maximum height to chord ratio (Y/C) at when the non-dimensional chord length (X/C) is approximately one third. An intermediate region follows the leading edge region and is characterized by a shallow convex region, followed by a flow reattachment surface at the trailing edge region characterized by a second concave region and a local maximum of the height to chord ratio at approximately four fifths of the non-dimensional chord length.
United States Patent Application Publication Number 2008/0095631, which was authored by Bertony, describes a vertical axis wind turbine comprising three vertically extending sails where each sail comprises a strip of substantially constant width. The opposite ends of each sail are longitudinally twisted to have a pitch angle of approximately 90 degrees. The turbine further comprises a vertically extending central core and a vertically extending opening between each sail and the core.
Also disclosed is an improvement in a vertical axis wind turbine having at least one main blade each of which has a longitudinal extent and a longitudinally extending radially outermost edge. The improvement comprises a longitudinally extending auxiliary blade spaced from the main blade to define a venturi inducing gap between the main blade and the auxiliary blade whereby the turbine has a zone of influence which extends radially beyond the maximum radial extent of the blades.
It will be seen from a review of the prior art that the art fails to disclose a turbine assembly having scoop-like tear drop shaped rotor blades or vanes for capturing fluid current directed thereagainst within a range of 155 rotational degrees. The prior art thus perceives a need for such a turbine or rotor assembly as described in more detail hereinafter.